It is common practice that a wellbore leading to a subterranean reservoir, especially a hydrocarbon reservoir, is lined with a casing which is cemented in place in the wellbore. Often a production tube is positioned inside the casing. From time to time it may become necessary to replace or repair these tubular components. This may be done because of corrosion of the tubing, with the risk of failure, or because of damage to the tubing or the discovery of leakage. By way of some illustrations, Society of Petroleum Engineers papers SPE 30984, 65014 and 92330 report instances of corrosion. SPE 92330 also mentions a need to repair damage arising through perforating gun misfire. SPE108757 recounts the repair of production casing suffering leakage.
Removal of tubing to repair or replace it is very expensive. Some techniques for repair in situ exist. The known techniques for repair include systems in which an expandable sleeve is inserted within the defective tubing and then expanded into contact with the inner surface of that tubing. Expandable systems were used for the repairs reported in SPE 87212 and SPE 1087574. U.S. Pat. Nos. 5,494,106, 5,695,008, 5,718,288 and 6044906 disclosed a system in which an expandable sleeve incorporating a fluid chemical composition is lowered to the required depth in the well by a wireline, expanded into contact with the tubing and then heated electrically to polymerise the composition to a solid state, so that the tubing is provided with a rigid ling of the polymerised composition reinforced by the fibrous supporting sleeve. The use of this system for a casing repair job was described in detail in SPE 68129. Its use to seal off perforations was described in SPE 56867 and its use to shut off water production was described in SPE 72051. This last document mentions that a specially developed polymerisable resin was required; it also mentions that the supply of electrical power to bring about polymerization was continued for some hours and required the wireline cable to be operated above its normal rating. WO98/59151 also disclosed an expandable sleeve impregnated with a polymerizable composition, and mentioned briefly that an alternative composition could be polymerizable by exposure to X-ray or uv radiation.
French published patent application FR 2780751A disclosed an alternative of impregnating the sleeve with polymerisable resin after it had been expanded within the wellbore.
Other processes using a polymerisable liquid composition have been disclosed in U.S. Pat. No. 6,969,427. This document described an earlier process in which a liquid coating was applied in an interval of tubing between two wiper plugs and polymerised to a rigid coating. The document noted difficulties with such a process and then went on to disclose its own invention in which separate components of a multipart curable system are delivered separately to a spray head which mixes them and applies them to the interior of tubing to be coated. Such a process dictates that the tubing concerned is empty while spraying is carried out and it is apparent from the text of the documnent that it envisages spraying through air or gas, not through liquid. Moreover, the provision of a plurality of paths for separate transport of the constituents of the composition will add to the cost of the equipment used if the transport pathways are long.